Development of 2400-2450 MHz Frequency Band RF Energy Harvesting System for Low-Power Device Operation.

Recently, there has been an increasing fascination for employing radio frequency (RF) energy harvesting techniques to energize various low-power devices by harnessing the ambient RF energy in the surroundings. This work outlines a novel advancement in RF energy harvesting (RFEH) technology, intending to power portable gadgets with minimal operating power demands. A high-gain receiver microstrip patch antenna was designed and tested to capture ambient RF residue, operating at 2450 MHz. Similarly, a two-stage Dickson voltage booster was developed and employed with the RFEH to transform the received RF signals into useful DC voltage signals. Additionally, an LC series circuit was utilized to ensure impedance matching between the antenna and rectifier, facilitating the extraction of maximum power from the developed prototype. The findings indicate that the developed rectifier attained a peak power conversion efficiency (PCE) of 64% when operating at an input power level of 0 dBm. During experimentation, the voltage booster demonstrated its capability to rectify a minimum input AC signal of only 50 mV, yielding a corresponding 180 mV output DC signal. Moreover, the maximum power of 4.60 µW was achieved when subjected to an input AC signal of 1500 mV with a load resistance of 470 kΩ. Finally, the devised RFEH was also tested in an open environment, receiving signals from Wi-Fi modems positioned at varying distances for evaluation.

RF energy harvesters for wireless sensors, state of the art, future prospects and challenges: a review.

The power consumption of portable gadgets, implantable medical devices (IMDs) and wireless sensor nodes (WSNs) has reduced significantly with the ongoing progression in low-power electronics and the swift advancement in nano and microfabrication. Energy harvesting techniques that extract and convert ambient energy into electrical power have been favored to operate such low-power devices as an alternative to batteries. Due to the expanded availability of radio frequency (RF) energy residue in the surroundings, radio frequency energy harvesters (RFEHs) for low-power devices have garnered notable attention in recent times. This work establishes a review study of RFEHs developed for the utilization of low-power devices. From the modest single band to the complex multiband circuitry, the work reviews state of the art of required circuitry for RFEH that contains a receiving antenna, impedance matching circuit, and an AC-DC rectifier. Furthermore, the advantages and disadvantages associated with various circuit architectures are comprehensively discussed. Moreover, the reported receiving antenna, impedance matching circuit, and an AC-DC rectifier are also compared to draw conclusions towards their implementations in RFEHs for sensors and biomedical devices applications.

A Retrospective Follow-Up Study To Show The Effectiveness Of Booster Dose Of Foam Sclerotherapy Session At 3rd And 6th Months In Preventing The Recurrence Of Varicose Veins.

BACKGROUND: Injection sclerotherapy administration is known to cause a decreased recurrence of varicose vein disease. This research aimed to investigate the recurrence of varicose vein disease after giving booster doses of injection sclerotherapy. The booster doses were given at 3rd and 6th months. METHODS: One hundred and fifty patients participated and all patient's included ages 30-70 in the category of 'low risk' patients. The patients were both males and females. Patients participating in the study were counselled appropriately and written consent was taken from them. Moreover, the patients selected were volunteers and agreed to be part of the study. Patients who were above 70 years of age, those who were at a high-risk due to some co-morbidities (high-risk patients), patients not willing to be part of the study, those allergic to drugs being used including sclerosant and people with any known psychiatric illness or cardiac arrhythmias, deep venous thrombosis patients, patients having arteriovenous malformation/venous ulcers were all excluded. If the patient was pregnant, the gynaecology team was taken on board and the procedure was carried out. Every procedure was carried out under the direct supervision of the supervisor. Booster dose sessions of Foam Sclerotherapy were held at 3rd and 6th months of the study time. Their effectiveness was observed and documentation was carried out. RESULTS: Since it was a procedure that could be done in the OPD, there was no need for specialized anaesthesia care. It is of significant notice that when a patient of varicose veins was given a booster intravenous sclerosant injection at 3rd and 6th month of treatment, chances of recurrence decreased to 50%.

Double Stab Excision Arteriotomy-A Novel Technique For A Better Outcome.

BACKGROUND: This study was carried out to introduce a new technique of excision arteriotomy and to compare it with standard excision arteriotomy in terms of achieving desired size, shape and margins with minimal technical problems. METHODS: This was a comparative study carried out at the Vascular Surgery Unit of Combined Military Hospital Peshawar between January and September 2022. A total of 150 patients of chronic renal failure undergoing Arteriovenous access fulfilling the inclusion criteria were enrolled in our study. The patients were randomized into two groups, 75 in each group: Group A consisted of patients who underwent Conventional excision arteriotomy and Group B underwent Double Stab excision Arteriotomy. The endpoint of the study was to achieve an appropriate arteriotomy of the desired size and shape by having regular margins without intimal dissection during its formation or otherwise inappropriate arteriotomy if any of the criteria is not met. RESULTS: Among the total 150 patients included in our study, Ages ranged between 30-60 years and a mean age of 52.5 years. There were 82 (54.66%) males and 68 (45.33%) females with a male-to-female ratio of 1.2:1. In group A (Conventional Excision arteriotomy) there were 30 (40%) inappropriate arteriotomies and 45 (60%) appropriate arteriotomies. Among the total 30(40%) inappropriate arteriotomies in group A, larger than desired size arteriotomies were 10 cases (33.33%) followed by smaller than desired size arteriotomies; 6 (20%), irregular margins 9 (30%), intimal dissection 3(10%) & lateral tear 2 (6.66%) respectively. In group B of double stab excision arteriotomies, appropriate arteriotomies were achieved in 69 (92%) while the rest had inappropriate arteriotomies in 6 (8%). Among the total 6 (8%) inappropriate arteriotomies in group B, larger than desired size arteriotomies were 2 (33.33%), smaller than desired size arteriotomy; 1 (16.66%), irregular margins 1 (16.66%), intimal dissection;2 (33.33%) & no lateral tear respectively. CONCLUSIONS: This study concluded that the Double stab excision arteriotomy technique is superior to the conventional excision arteriotomy technique. The advantages of our technique are; its reliability with a short learning curve and can be performed precisely and safely.

Analytical Modeling and Simulation of an Electromagnetic Energy Harvester for Pulsating Fluid Flow in Pipeline.

This paper presents the analytical modeling and simulation of an electromagnetic energy harvester (having linear behaviour) that generates power from pulsating fluid flow for pipeline condition monitoring systems. The modeled energy harvester is comprised of a cylindrical permanent magnet and a wound coil attached to a flexible membrane which oscillates due to the pulsating fluid flow in the pipe over which the prototype is considered to be mounted. In the harvester electrical energy is produced due to the relative motion between the coil and magnet. Based on the harvester's architecture a lumped parameter model (single degree of freedom system) is developed and is simulated at different physical operational conditions. The simulation is performed at pressure amplitude of 625 Pa. When subjected to the operational frequency sweep, at the harvester's resonant frequency (500 Hz) and damping ratio of 0.01, the devised model predicted the maximum open circuit voltage of 2.55 V and load voltage of 1.27 V. While operating under resonance, the maximum load voltage of 2.45 V is estimated at load resistance of 100 Ω. However, at an optimum load of 4.3 Ω, the simulation shows a production of 188151.2 µW power at a frequency of 500 Hz.

Elemental analysis of ten plant species at three phenological stages.

Livestock rearing is a common practice in Tehsil Takht-e-Nasrati by the locals to earn their livelihood. Low productivity due to poor health of livestock is major consideration in the study area. In order to know whether this low productivity and poor health might be due to poor quality of forage, ten plant species were analyzed for micro mineral quantification at three phenological stages. Mineral compositions of plants are used to diagnose probable deficiencies in food and forage and nutritional status of plants. Comparison among at vegetative stage of test species and micro nutrients showed that the amount of manganese was found high (64.4mg & &Kg-1) in Chrozophora obliqua. Comparison among at reproductive and post reproductive stages of test species and micro nutrients pointed out that the amount of nickel was found high (67.24mg & Kg-1) and (80.4mg & Kg-1) respectively in Vitex trifolia. It is concluded that micro-minerals concentrations available in these forage plants to the grazing livestock were very low, hence this may be, one of the causes responsible for the pitiable health and productivity of the grazing animals in investigated area.

Energy Harvesting from the Stray Electromagnetic Field around the Electrical Power Cable for Smart Grid Applications.

For wireless sensor node (WSN) applications, this paper presents the harvesting of energy from the stray electromagnetic field around an electrical power line. Inductive and capacitive types of electrodynamic energy harvesters are developed and reported. For the produced energy harvesters, solid core and split-core designs are adopted. The inductive energy harvester comprises a copper wound coil which is produced on a mild steel core. However, the capacitive prototypes comprise parallel, annular discs separated by Teflon spacers. Moreover, for the inductive energy harvesters' wound coil and core, the parametric analysis is also performed. A Teflon housing is incorporated to protect the energy harvester prototypes from the harsh environmental conditions. Among the inductive energy harvesters, prototype-5 has performed better than the other harvesters and produces a maximum rms voltage of 908 mV at the current level of 155 A in the power line. However, at the same current flow, the capacitive energy harvesters produce a maximum rms voltage of 180 mV. The alternating output of the prototype-5 is rectified, and a super capacitor (1 F, 5.5 V) and rechargeable battery (Nickel-Cadmium, 3.8 V) are charged with it. Moreover, with the utilization of a prototype-5, a self-powered wireless temperature sensing and monitoring system for an electrical transformer is also developed and successfully implemented.

Contributed Review: Recent developments in acoustic energy harvesting for autonomous wireless sensor nodes applications.

Rapid developments in micro electronics, micro fabrication, ultra-large scale of integration, ultra-low power sensors, and wireless technology have greatly reduced the power consumption requirements of wireless sensor nodes (WSNs) and make it possible to operate these devices with energy harvesters. Likewise, other energy harvesters, acoustic energy harvesters (AEHs), have been developed and are gaining swift interest in last few years. This paper presents a review of AEHs reported in the literature for the applications of WSNs. Based on transduction mechanism, there are two types of AEHs: piezoelectric acoustic energy harvesters (PEAEHs) and electromagnetic acoustic energy harvesters (EMAEHs). The reported AEHs are mostly characterized under the sound pressure level (SPL) that ranges from 45 to 161 dB. The range for resonant frequency of the produced AEHs is from 146 Hz to 24 kHz and these produced 0.68 × 10(-6) µW to 30 mW power. The maximum power (30 mW) is produced by a PEAEH, when the harvester is subjected to a SPL of 161 dB and 2.64 kHz frequency. However, for EMAEHs, the maximum power reported is about 1.96 mW (at 125 dB and 143 Hz). Under the comparable SPLs, the power production by the reported EMAEHs is relatively better than that of PEAEHs, moreover, due to lower resonant frequency, the EMAEHs are more feasible for the low frequency band acoustical environment.

Hybrid acoustic energy harvesting using combined electromagnetic and piezoelectric conversion.

This paper reports a novel hybrid acoustic energy harvester. The harvester utilizes both the electromagnetic and piezoelectric conversion mechanisms simultaneously to convert the ambient acoustical noise into electrical power for self-powered wireless sensor nodes. The proposed harvester is comprised of a Helmholtz resonator, two magnets mounted on a piezoelectric plate, and a wound coil located under the magnets. The harvester is characterized both under harmonic and real random acoustical excitations. In-lab, under harmonic acoustical excitation at a sound pressure level of 130 dB and frequency of 2.1 kHz, an optimum power of 2.86 µW (at 114 Ω optimum load) is obtained from electromagnetic conversion and 50 µW (at 1000 Ω optimum load) is generated by the piezoelectric harvester's part. Moreover, in real acoustical environment of a domestic electric generator the peak voltages of 40 and 123 mV are produced by the electromagnetic and piezoelectric portions of the acoustic energy harvester.

Experimental study of direct laser deposition of Ti-6Al-4V and Inconel 718 by using pulsed parameters.

Laser direct metal deposition (LDMD) has developed from a prototyping to a single metal manufacturing tool. Its potential for creating multimaterial and functionally graded structures is now beginning to be explored. This work is a first part of a study in which a single layer of Inconel 718 is deposited on Ti-6Al-4V substrate. Single layer tracks were built at a range of powder mass flow rates using a coaxial nozzle and 1.5 kW diode laser operating in both continuous and pulsed beam modes. This part of the study focused on the experimental findings during the deposition of Inconel 718 powder on Ti-6Al-4V substrate. Scanning electron microscopy (SEM) and X-ray diffraction analysis were performed for characterization and phase identification. Residual stress measurement had been carried out to ascertain the effects of laser pulse parameters on the crack development during the deposition process.